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Putting a Cell Together
Published in Thomas M. Nordlund, Peter M. Hoffmann, Quantitative Understanding of Biosystems, 2019
Thomas M. Nordlund, Peter M. Hoffmann
In higher eukaryotes, cell division (mitosis) requires partial or complete breakdown of the nuclear envelope, disassembly of nuclear pore complexes, and formation of mitotic “spindles.” This last process, spindle formation, requires involvement of microtubules and molecular motors to form the structures. The nuclear envelope reforms and then encloses the chromosomes later. The traditional rule in lower eukaryotes, like yeast, has been that the envelope remains intact. The cited studies on Ostreococcus, however, show that its nuclear envelopes are mostly open, so the “rules” are not followed in every organism: gaps hundreds of nanometers in size were observed in most stages of cell growth. In some rare cases, the nuclear membrane did not come close to enclosing the DNA in the nucleus. We will not investigate the complicated process of cell division any further, but it is clear that major forces are involved—forces that require a sufficient magnitude, but more importantly, the organization and synchronization of those forces. A serious study of these processes is well beyond the scope of this text. A review of this sort of coordination of forces can be found in the article by J. Howard,14 to which we will return in Chapter 16.
Toward Understanding the Intelligent Properties of Biological Macromolecules
Published in George K. Knopf, Amarjeet S. Bassi, Smart Biosensor Technology, 2018
At the Center for Intelligent Biomaterials, we have taken the approach that DNA sequence-based parameters, such as PD, provide a simple and potentially useful way to eventually understand the intelligent properties underlying DNA–protein energetics and stability. Therefore, we have initially carried out studies to establish whether the PD scale provides insight into the energetic stability of single base pair variants of a specific DNA sequence interacting with their recognition protein. The DNA–protein system we studied is that shown inset in Figure 2.43, the relatively simple yeast kinetochore, a centromere DNA–multiprotein complex responsible for binding to the microtubules of the yeast mitotic spindle (168). The result of this binding is correct segregation into daughter cells of each of the 16 yeast chromosomes during cell division. In this system, we have focused on two particular conserved sequence DNA–protein interactions. The first is between the short symmetric DNA sequence labeled CDEI and the dimeric protein CBF1. The second is between the longer symmetric CDEIII DNA and a complex of binding proteins labeled CBF 3. As shown in the inset schematic, these complexes are in close proximity, since they occur wrapped to form a modified centromere nucleosome found at the CEN sequence location on each yeast chromosome. Both complexes subsequently participate in the self-assembly of a complex multiprotein, multi-DNA sequence kinetochore on each chromosome. This large complex binds a long spindle microtubule in the cell, which then correctly segregates the chromosome during cell division.
Proteomic analysis of whole-body responses in medaka (Oryzias latipes) exposed to benzalkonium chloride
Published in Journal of Environmental Science and Health, Part A, 2020
Young Sang Kwon, Jae-Woong Jung, Yeong Jin Kim, Chang-Beom Park, Jong Cheol Shon, Jong-Hwan Kim, June-Woo Park, Sang Gon Kim, Jong-Su Seo
Microtubule-associated protein (spot 3) was significantly upregulated in BAC-exposed medaka. Microtubule-associated proteins are involved in microtubule dynamics and are essential for mitotic spindle formation and mitosis progression. Furthermore, microtubule-associated proteins play an essential role in the early developmental stages of zebrafish.[60] Also, microtubule-associated proteins are involved in the regulation of the immune response signaling of microtubules that construct eukaryotic cells and the cytoskeleton.[61] Recent evidence suggests that classical microtubule-associated proteins also guide motor protein transport, interact with the actin cytoskeleton, and are involved in various neuronal signaling networks.[62]
Les vertus des défauts: The scientific works of the late Mr Maurice Kleman analysed, discussed and placed in historical context, with particular stress on dislocation, disclination and other manner of local material disbehaviour
Published in Liquid Crystals Reviews, 2022
In cell biology, the so-called mitotic spindle describes the state of a eukaryotic cell during cell division. We remind the reader that eukaryotes are often (not always, although the reverse is the case) multi-cellular organisms with the property that the genetic material (chromosomes are contained inside a nucleus which is bounded by the nuclear envelope consisting a lipid bilayer. During cell division microtubules (long polymers) align between two spindle poles which act as the organising centres for the new nuclei. The separated (‘single helix’) chromosomes travel along the aligned microtubules to the spindle poles, eventually creating identical daughter cells.